1. Field of the Invention
The present invention relates to short-range RF networks and, more particularly, to client communication as a client roams through the network.
2. Description of the Related Art
The availability of various types of communication devices produces a need to have these devices interact with each other in a manner which is cost efficient and which can be easily implemented. Such communication can occur between two or more terminal devices (e.g. telephones, computers, printers, facsimile machines, personal digital assistants (PDAs), etc.) by wired connection such as by connecting electrical conductors to the devices, or by wireless communication using infrared signals or radio frequency (RF) signals. For many applications, RF signals are preferred as they do not require line-of-sight interaction between a transmitter and a receiver of a terminal device pair.
Recently, low power RF systems have been proposed for providing communications among a plurality of transceivers through a short range communication link. One such short-range RF technology is currently under development and is known as “Bluetooth”. This system will be commercially available in the near future and it operates in the open spectrum around 2.45 GHz. This unlicensed radio band, known as the Industrial-Scientific-Medical (ISM) band, is globally available. The operating range of the Bluetooth RF system is approximately 10 meters for a normal power mode, and has proven to be economically efficient.
Depending on the available bandwidth of the country, (in parts of Europe and the U.S., a bandwidth of 83.5 MHz. is available, which is wider than the band available in Japan, Spain, and France) either 79 or 23 RF channels are used, the channel separation being 1 MHz. The channel is represented by a pseudo-random hopping sequence through the 79 or 23 RF channels. The hopping is unique in a small area, called a piconet. One of the Bluetooth devices in the piconet functions as a master and the others as slaves.
Each channel is further divided into time slots, each 625 ls in duration, during which packets can be transmitted by the master and slaves. It is planned that Bluetooth chips having the described characteristics will be installed in various kinds of electronic devices for enabling communication among the separate devices.
Wireless relay networks also exist which, in effect, extend an operating range of a local RF system by utilizing relay devices to interface with and provide communication between two or more terminal devices. Such a network is disclosed in PCT Application No. WO 98/17032 wherein a plurality of communication nodes are wirelessly connected to each other and to a host device for providing numerous communication links for data to be communicated between the host and terminal devices interfaced with the nodes.
Such systems, when deployed in such places as department stores and shopping malls, have been extended to provide unsolicited advertising and promotional messages to terminal devices. Such systems have also been extended to include Internet servers which allow a terminal device connected to the short-range wireless relay network to initiate an Internet session. However, such systems experience drawbacks when a user on a terminal device roams from the coverage area of one transceiver into the coverage area of another. One drawback of such a system is that a terminal device's Internet address changes as it roams from one node's coverage area into another, effectively terminating any Internet sessions that may have been in progress, thereby requiring new Internet connections to be made as the terminal device roams. Another drawback of such a system is that local content supplied to a terminal device according to its location when it initiated communication may no longer be appropriate after it roams to a different transceiver's coverage area.